When two instances of QtCreator are running simultaneously, the settings for manually added QtVersions disappears or gets corrupted under "Options" -> "Build & Run" -> "QtVersions"

Additionally, any cloned build settings under "Projects" -> "Build & Run" -> "QtVersion" -> "Build Settings"  are corrupted/deleted.

I have no need for running multiple instances, but for some reason, the windows start menu sometimes seems to start QtCreator up twice on a single click. 

Therefor for me it would be a sufficient fix to just prevent dual instances, but I assume other users might not agree.

Reproduce:

Add static Qt library to build settings

Set up new project

Clone Debug setting to MY_DEBUG, and set some additional environment vars.

Close Qt Creator

Start Qt Creator instance one

Start Qt Creator instance two

Select default in start up dialog of instance one

Close both instances 

The next time Qt Creator is opened, the settings will be corrupted.